What would they feel? Wouldn't it just be a higher grade of rubber that isn't prone to cracking? Or are they making the boots larger?

They wouldn't be accordioned/ribbed, they'd be smooth, thats one benefit I can think of. They won't crack, won't get hard and brittle, aren't going to be hurt by heat, and I'm sure theres more benefits. This is the kind of thing thats a permanent replacement for a part that is unfortunately a normal wear part.